Three dimensional printing system that automatically removes particles from build plane

ABSTRACT

A three dimensional printing system includes a resin vessel, a light engine, a movement mechanism, a support fixture, and a controller. The resin vessel is for containing a photocurable resin and has a lower portion with a transparent sheet. The light engine is configured to selectively project radiation up through the transparent sheet and over a build plane. The support fixture is coupled to the movement mechanism and has a lower rim that surrounds a central opening and faces the transparent sheet. The controller is configured to: (1) operate the movement mechanism to position the rim at an operating distance from the transparent sheet, (2) operate the light engine and the movement mechanism to form a particle trapping sheet that spans the central opening, and (3) operate the light engine and the movement mechanism to form the three dimensional article.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application is a continuation-in-part ofU.S. application Ser. No. 15/926,148, Entitled “THREE DIMENSIONALPRINTING SYSTEM THAT AUTOMATICALLY REMOVES PARTICLES FROM BUILD PLANE”,by Christopher Tanner et al., filed on Mar. 20, 2018 which is herebyincorporated by reference. U.S. application Ser. No. 15/926,148 claimspriority to U.S. Provisional Application Ser. No. 62/477,747, Entitled“THREE DIMENSIONAL PRINTING SYSTEM THAT AUTOMATICALLY REMOVES PARTICLESFROM BUILD PLANE” by Christopher Tanner et al., filed on Mar. 28, 2017,incorporated herein by reference under the benefit of U.S.C. 119(e).

FIELD OF THE INVENTION

The present disclosure concerns an apparatus and method for fabricationof solid three dimensional (3D) articles of manufacture from radiationcurable (photocurable) resins. More particularly, the present disclosureimproves the quality of a three dimensional (3D) article of manufacturethrough the removal of particles extending into a build plane.

BACKGROUND

Three dimensional (3D) printers are in rapidly increasing use. One classof 3D printers includes stereolithography printers having a generalprinciple of operation including the selective curing and hardening ofradiation curable (photocurable) liquid resins. A typicalstereolithography system includes a containment vessel holding thephotocurable resin, a movement mechanism coupled to a support surface,and a controllable light engine. The stereolithography system forms athree dimensional (3D) article of manufacture by selectively curinglayers of the photocurable resin.

In one system embodiment the vessel includes a transparent sheet thatforms part of a lower surface of the vessel. The support surface ispositioned above and in facing relation with the transparent sheet. Thefollowing steps take place: (1) The movement mechanism positions thesupport surface whereby a thin layer of the photocurable resin residesbetween the support surface and the transparent sheet. (2) The lightengine transmits pixelated light up through the transparent sheet toselectively cure a layer of the photocurable resin proximate to and ontothe support surface. The focus of the pixelated light curing is referredto a “build plane.” (3) The movement mechanism then incrementally raisesthe support surface. Steps (2) and (3) are repeated to form a threedimensional (3D) article of manufacture having a lower face in facingrelation with the transparent sheet.

One difficulty is an accumulation of particles on the transparent sheetand/or within the photocurable resin. The particles are formed from thephotocurable resin and are the result of portions of a fabricatedarticle that may break off and settle into the resin. A required gapbetween the build plane and the transparent sheet is very small. Thelower face of the support surface or three dimensional article ofmanufacture must therefore be positioned very close (a small fraction ofa millimeter typically) to the transparent sheet in order to performstep (2) above. During this positioning, the accumulated particles canbecome compressed between the transparent sheet and the lower face.These particles can be compressed and can damage the transparent sheetand become embedded in the three dimensional article of manufacture,possibly creating a defect. Damage to the transparent sheet will affectits light transmissive properties and therefore impact the quality ofall subsequent fabrication. The transparent sheet is also expensive anddisruptive to replace. What is needed is a system and method tofacilitate particle removal.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram schematic of an exemplary embodiment of athree dimensional printing system for forming a three dimensionalarticle of manufacture.

FIG. 2A is a block diagram schematic depicting a print engine and afirst embodiment of a configuration whereby the print engine trapsdeleterious particles.

FIG. 2B is a block diagram schematic depicting a print engine and asecond embodiment of a configuration whereby the print engine trapsdeleterious particles.

FIG. 2C is a block diagram schematic depicting a print engine and athird embodiment of a configuration whereby the print engine trapsdeleterious particles.

FIG. 3 is a plan view schematic of an exemplary fixture for supporting aparticle trapping sheet.

FIG. 4 is a sectional view taken from AA′ of FIG. 3 with an exemplaryparticle trapping sheet included.

FIG. 5 is a schematic plan view of an exemplary particle trapping sheet.

FIG. 5A is a cross sectional view of an exemplary particle trappingsheet taken through BB′ of FIG. 5. This particle trapping sheetembodiment corresponds to FIG. 2A.

FIG. 5B is a cross sectional view of an exemplary particle trappingsheet taken through BB′ of FIG. 5. This particle trapping sheetembodiment corresponds to FIG. 2B.

FIG. 6A is a flowchart depicting a first embodiment of a process foroperating printing system 2 which corresponds to FIG. 2A.

FIG. 6B is a flowchart depicting a second embodiment of a process foroperating printing system 2 which corresponds to FIG. 2B.

FIG. 6C is a flowchart depicting a third embodiment of a process foroperating printing system 2 which corresponds to FIG. 2C.

FIG. 7A is a schematic block diagram depicting an embodiment of astandalone print engine forming a particle trapping sheet.

FIG. 7B is a schematic block diagram depicting an embodiment of astandalone print engine manufacturing a three dimensional article.

FIG. 8 is a flowchart depicting an embodiment of a method ofmanufacturing a three dimensional article.

FIG. 9A is an isometric drawing of an alternative embodiment of asupport fixture having a central opening.

FIG. 9B is a side cutaway view of the support fixture of FIG. 9A.

FIG. 10A is a cross-sectional view of the support fixture of FIG. 9A.

FIG. 10B is a cross-sectional view of the support fixture of FIG. 10Awith an addition of a particle trapping sheet.

FIG. 10C is a cross-sectional view of the support fixture of FIG. 10Awith additions of a particle trapping sheet and a three dimensionalarticle.

FIG. 11 is a flowchart that represents an embodiment of a method formanufacturing a three dimensional article that utilizes the supportfixture 40 of FIGS. 9A and 9B.

FIG. 12 is a cross-sectional view of a support fixture with a firstembodiment of a particle trapping sheet that can be formed according tosteps 152-156 of method 150 of FIG. 11.

FIG. 13 is a cross-sectional view of a support fixture with a secondembodiment of a particle trapping sheet that can be formed according tosteps 152-156 of method 150 of FIG. 11.

FIG. 14 is cross sectional view of a support fixture with a thirdembodiment of a particle trapping sheet that can be manufacturedaccording to the method 150 of FIG. 11.

FIG. 15A depicts a peripheral support that has been formed onto asupport fixture.

FIG. 15B depicts an upper layer of a particle trapping sheet.

FIG. 15C depicts a middle layer of a particle trapping sheet.

FIG. 15D depicts a lower layer of a particle trapping sheet.

SUMMARY

In a first aspect of the disclosure, a three dimensional printing systemis for manufacturing a three dimensional article. The three dimensionalprinting system includes a resin vessel, a light engine, a movementmechanism, a support fixture, and a controller. The resin vessel is forcontaining a photocurable resin and has a lower portion with atransparent sheet. The light engine is configured to selectively projectradiation up through the transparent sheet and over a build plane. Thesupport fixture is coupled to the movement mechanism and includes anupper portion for coupling to the movement mechanism, a lower portionwith a rim surrounding a central opening, and a side wall coupling theupper and lower portions. The controller is configured to: (1) operatethe movement mechanism to position the rim at an operating distance fromthe transparent sheet, (2) operate the light engine and the movementmechanism to form a particle trapping sheet that spans the centralopening, and (3) operate the light engine and the movement mechanism toform the three dimensional article attached to and below the particletrapping sheet.

In one implementation the controller is further configured to operatethe light engine to form a peripheral support along the rim afterpositioning the rim at the operating distance but before forming theparticle trapping sheet. The peripheral support can have a shape muchlike a rectangular frame. Alternatively, the peripheral support can havea zig-zag shape alternating shape along the rim.

In another implementation, the particle trapping sheet includes taperingfeatures that taper between the particle trapping sheet and the threedimensional article to facilitate removal of the three dimensionalarticle from the particle trapping sheet.

In yet another implementation, the particle trapping sheet defines anarray of conduits to allow resin to flow through the particle trappingsheet and through the central opening as the movement mechanism raisesand lowers the support fixture. The conduits individually are at leastpartially oriented at an oblique angle with respect to a vertical axisto facilitate complete trapping of particles.

In a further implementation, the particle trapping sheet defines anarray of conduits to allow resin to flow through the particle trappingsheet and through the central opening as the movement mechanism raisesand lowers the support fixture. The conduits individually define anupper opening on an upper side of the particle trapping sheet and alower opening on a lower side of the particle trapping sheet, the upperand lower openings are laterally offset to facilitate trapping ofparticles.

In a yet further implementation, the particle trapping sheet has atleast a vertical thickness of one millimeter to provide structuralsupport for the three dimensional article.

In another implementation, the particle trapping sheet includes aplurality of support ribs to provide structural support for the threedimensional article. The support ribs can be defined between an uppersheet and a lower sheet that are thinner vertically than the supportribs.

In a second aspect of the disclosure, a three dimensional printingsystem includes a resin vessel, a light engine, a movement mechanism, afixture, and a controller. The resin vessel is for containing aphotocurable resin and has a lower portion with a transparent sheet. Thelight engine is configured to selectively project radiation up throughthe transparent sheet and over a build plane. The fixture is coupled tothe movement mechanism and has a lower face that faces the transparentsheet. The controller is configured to operate the light engine tosolidify a particle trapping sheet proximate to the build plane therebytrapping particles that extend upwardly from the transparent sheet intothe build plane.

In one implementation the particle trapping sheet is solidified andformed while the fixture is in a raised position above the resin vesselin which the lower face of the fixture is not in contact with the resin.

In another implementation the controller is configured to pauseoperation of the print engine to allow removal of the particle trappingsheet from the resin vessel before the lower face of the fixture islowered into the resin.

In yet another implementation the three dimensional printing systemincludes a user interface device. The controller is configured todisplay instructions on a user interface that instruct a user to removethe particle trapping sheet from the resin vessel.

In a further implementation the three dimensional printing systemincludes a user interface device. The controller is configured to pauseoperation of the print engine to allow removal of the particle trappingsheet from the resin vessel before the lower face of the fixture islowered into the resin. The controller is also configured to receiveinstructions from a user interface to restart operation of the printengine. The controller is then configured to lower the fixture until thelower face is positioned within the resin and proximate to the buildplane and operate the light engine and movement mechanism to manufacturethe three dimensional article onto the lower face.

In a third aspect of the disclosure, a three dimensional printing systemincludes a print engine, a fixture, and a controller. The print enginefurther includes a vessel, a light engine, and a movement mechanism. Thevessel is for containing a photocurable resin and has a lower portionwith a transparent sheet defining at least part of a lower surface ofthe vessel. The light engine is configured to project radiation upthrough the transparent sheet over a lateral build plane which defines amaximum addressable lateral range of the light engine. The fixture has alower face that faces downwardly. The controller is configured to: (1)position the lower face of the fixture at the build plane which is at anoperating distance from the transparent sheet, and (2) operate the lightengine and movement mechanism to solidify a particle trapping sheetproximate to the transparent sheet and substantially spanning the buildplane and to thereby trap particles that are present along the buildplane.

In one implementation the controller includes a processor coupled to aninformation storage device. The information storage device includes anon-transient or non-volatile storage device storing instructions that,when executed by the processor, control the light engine and themovement mechanism. The controller can be at one location or distributedamong a plurality of locations in the printing system. In a firstembodiment the controller is entirely within the print engine whichoperates as a standalone three dimensional printer. In a secondembodiment the controller includes a control server that controls theoverall printing system and a print engine controller that is locatedwithin the print engine. In the second embodiment the three dimensionalprinting system includes various modules including one or more of afixture cassette, a post processing station, an inspection station, anda robotic transport mechanism for transporting the fixture between themodules.

In another implementation the fixture has a lower end defining arecessed surface from which a plurality of projections extend downwardlyfrom the recessed surface to distal tips. The particle trapping sheetdefines an upper surface coupled to the distal tips and an opposed lowersurface. The opposed lower surface further defines a plurality oftapering features. The controller is further configured to operate thelight engine and the movement mechanism to form a three dimensionalarticle of manufacture that is coupled to the tapering features. Thetapering features minimize a surface area of connection between thethree dimensional article of manufacture and the particle trapping sheetin order to facilitate the later physical separation of the particletrapping sheet from the three dimensional article of manufacture.

In yet another implementation the printing system includes a transportmechanism and the controller is further configured to: (3) unload thefixture from the print engine, (4) load a new fixture into the printingsystem, and (5) operate the light engine and the movement mechanism toform a three dimensional article of manufacture. The fixture used insteps (1) and (2) is a disposable fixture that is used exclusively forforming the particle trapping sheet and removing particles. Thedisposable fixture has a lower end defining a recessed surface fromwhich a plurality of projections extend downwardly from the recessedsurface to distal tips. An upper surface of the particle trapping sheetis formed onto the distal tips. The fixture used in steps (3) to (5) isa reusable fixture that is used entirely for forming three dimensionalarticles of manufacture.

In a further implementation the controller is configured to operate thelight engine and the movement mechanism to form a three dimensionalarticle of manufacture onto the fixture before forming the particletrapping sheet. The particle trapping sheet includes a plurality ofupwardly extending extensions that form a framework for supporting theparticle trapping sheet onto the three dimensional article ofmanufacture.

In a yet further implementation the particle trapping sheet has an uppersurface and an opposed lower surface. The particle trapping sheetdefines at least one opening passing from the upper surface to theopposed lower surface to provide flow of photocurable resin therethroughwhen the movement mechanism is raising or lowering the fixture.Preferably the at least one opening includes an array or plurality ofopenings that are laterally distributed across the particle trappingsheet.

In another implementation the particle trapping sheet includes a thinparallelepiped portion covering most or essentially all of the lateralarea of the build plane. The thickness is minimized so as to minimize arequired amount of resin for fabricating the particle trapping sheet.The particle trapping sheet also includes a framework of ribs orthickened portions to provide mechanical support for the thinparallelepiped portion. In some embodiments the particle trapping sheetincludes tapering features and/or extensions for coupling to a threedimensional article of manufacture. The coupling occurs at a narroweddistal tip. The tapering features and/or extensions can be laterallyaligned with the ribs so as to improve structural integrity. The thinparallelepiped portion can define openings therethrough to allow a flowof photocurable resin therethrough to facilitate vertical movement ofthe fixture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram schematic of an exemplary embodiment of athree dimensional printing system 2 for forming three dimensionalarticles of manufacture. Three dimensional printing system 2 includesfixture cassettes 4, print engines 6, post-processing stations 8,inspection stations 10, a transport mechanism 12, and a control server14.

A fixture cassette 4 stores a stack of fixtures that are utilized inprint engine 6, post-process stations 8, and inspection station 10. Insome embodiments there are different fixtures stored in differentfixture cassettes 4. One stack of fixtures can be disposable andutilized for a particle removal process. Another stack of fixtures canbe reusable and utilized for the formation and transport of a threedimensional article of manufacture.

An embodiment of print engine 6 will be described in further detail withrespect to FIGS. 2A, 2B, and 2C. Post process stations 8 are for addedprocesses for a three dimensional article of manufacture after it isformed. Post processing stations can include rinsing and cleaningstations, drying stations, and curing stations, to name some examples.Inspection stations 10 can be utilized to inspect for defects and/or tomeasure critical dimensions for a three dimensional article ofmanufacture after fabrication and post processing is complete.

Transport mechanism 12 is configured to pick up a fixture from a fixturecassette 4 and to transfer it to a print engine 6. Transport mechanism12 also transfers the fixture to the post process stations 8 and to theinspection stations 10. In one embodiment, the transport mechanismincludes a robotic gripper that can move in three axes.

FIG. 2A is a schematic block diagram depicting print engine 6 and afirst embodiment through which print engine 6 removes deleteriousparticles. In this and other figures, mutually perpendicular axes X, Yand Z will be used. Axes X and Y are lateral axes. In some embodiments Xand Y are also horizontal axes. Axis Z is a central axis. In someembodiments Z is a vertical axis. In some embodiments the direction +Zis generally upward and the direction −Z is generally downward.

Print engine 6 includes a vessel 16 containing photocurable resin 18.Vessel 16 includes a transparent sheet 20 that defines at least aportion of a lower surface 22 of vessel 16. A light engine 24 isdisposed to project light up through the transparent sheet 20 toselectively cure the photocurable resin 18 during formation of a threedimensional article of manufacture 26. Light engine 24 includes lightsource 28 and spatial light modulator 30.

Between a lower face 32 of the three dimensional article of manufacture26 and the transparent sheet 20 is a thin layer 34 of photocurable resin18. As the light engine 24 operates, a portion of the thin layer 34 ofphotocurable resin 18 is cured and solidified at and proximate to abuild plane 36. Build plane 36 defines a lateral extent (along X and Y)of a layer of photocure resin that the light engine 24 is capable ofcuring when forming the three dimensional article of manufacture 26.

Print engine 6 also includes a vertical movement mechanism 38 coupled toa fixture 40. Fixture 40 is for supporting the three dimensional articleof manufacture 26. Fixture 40 includes a lower end 42 having an upwardlyrecessed surface 44 and projections 46 that extend downwardly from therecessed surface 44.

Print engine 6 includes print engine controller 48 that is under controlof control server 14 and is coupled to light engine 24 and to verticalmovement mechanism 38. In the illustrated embodiment, the print enginecontroller 48 controls the light engine 24 and the movement mechanism 38to form a particle trapping sheet 50 before forming the threedimensional article of manufacture 26. The particle trapping sheet 50 isfirst formed at and proximate to the build plane 36 and just above thetransparent sheet 20. During formation of the particle trapping sheet 50the deleterious particulates are “bound up” in the particle trappingsheet 50 so that they are removed from the vicinity of the transparentsheet 20 to prevent build-up of particles and subsequent damage. Thelateral extent of the particle trapping sheet 50 is preferablysubstantially the entire build plane 36.

The particle trapping sheet 50 includes tapering features 52 that taperbetween the particle trapping sheet 50 and the three dimensional articleof manufacture 26. These tapering feature 52 facilitate removal of theparticle trapping sheet 50 from the three dimensional article ofmanufacture 26 after processing is complete.

FIG. 2B is a schematic block diagram depicting print engine 6 and asecond embodiment through which print engine 6 removes deleteriousparticles. In comparing FIGS. 2A and 2B, like reference numeralsindicate like elements. The discussion for FIG. 2B will be limited tothose features that necessarily make it different than FIG. 2A.

In the illustrated embodiment of FIG. 2B, the print engine controller 48controls the light engine 24 and the movement mechanism 38 to form athree dimensional article of manufacture 26 before forming a particletrapping sheet 50. The particle trapping sheet 50 includes extensions 54that form a framework for coupling the particle trapping sheet 50 to thethree dimensional article of manufacture 26. As with FIG. 2A, theparticle trapping sheet 50 preferably covers the entire build plane 36of light engine 24.

FIG. 2C is a schematic block diagram depicting print engine 6 and athird embodiment through which print engine 6 removes deleteriousparticles. In comparing FIGS. 2A, 2B, and 2C, like reference numeralsindicate like elements. The discussion for FIG. 2C will be limited tothose features that necessarily make it different than FIGS. 2A and 2C.

In the illustrated embodiment of FIG. 2C, the fixture 40 is a disposablefixture 40 that is used entirely for forming the particle trapping sheet50 to remove the deleterious particles. Other than being disposable, thefixture 40 is similar to the fixture 40 illustrated with respect to FIG.2A and includes the upwardly recessed surface 44 from which theprojections 46 extend downwardly.

FIG. 3 is a plan view schematic of fixture 40 looking upwardly in the +Zdirection. The fixture 40 is shown having a recessed surface 44 fromwhich projections 46 extend in the downward −Z direction. While theillustrated embodiment depicts nine projections 46 it is to beunderstood that any number of projections 46 can be employed. The use ofclosely spaced projections 46 can allow a reduction in the thickness andrigidity of the particle trapping sheet 50 because an unsupporteddistance is thereby reduced. The fixture 40 also includes openings 56for allowing the photocurable resin 18 to pass through the fixture 40 asit is raised and lowered in the vessel 16.

FIG. 4 is a cross-sectional view of fixture 40 taken through AA′ of FIG.3. FIG. 4 also includes the particle trapping sheet 50 which has beenformed onto the projections 46 of the fixture 40. The projections 46taper in downward −Z direction toward a distal end 58. Having a distalend 58 with a smaller cross sectional area reduces the impact of theprojections 46 upon particles that are proximate to the transparentsheet 20.

FIG. 5 is a schematic plan view of an exemplary particle trapping sheet50. FIG. 5A is a cross section of a first embodiment of the particletrapping sheet 50 that corresponds to the embodiment depicted in FIG.2A. The particle trapping sheet 50 includes a thin parallelepipedportion 60 covering most or essentially all of a lateral area of thebuild plane 36. Minimizing the thickness of the thin parallelepipedportion 60 minimizes an amount of photocurable resin required tofabricate the particle trapping sheet 50. The particle trapping sheet 50also includes thicker sections or ribs 62 that form a frame forsupporting the thin parallelepiped portion 60. The particle trappingsheet 50 also includes tapering features 52 for attachment to the threedimensional article of manufacture 26. The tapering geometry of thetapering features 52 minimizes a lateral area of contact between theparticle trapping sheet 50 and the three dimensional article ofmanufacture 26 to facilitate their later separation. The taperingfeatures 52 are preferably laterally aligned with ribs 62 to improvestructural integrity. The thin parallelepiped portion 60 also definesopenings 64 that allow the flow of the photocurable resin 18 as theparticle trapping sheet 50 is raised or lowered in the vessel 16. Inthis embodiment the particle trapping sheet 50 is attached to thefixture 40 at an upper side and to the three dimensional article ofmanufacture at a lower side defined by the tapering features 52 as inFIG. 2A.

While only a few openings 64 are shown, it is to be understood that alarge number of such openings 64 can be defined. The openings can beangled or stepped whereby particles are trapped at the lateral positionsof the openings 64. With a large number of openings 64, they can have arelatively small lateral dimensions to further enhance particle trappingin their vicinity.

FIG. 5B is a cross section of a second embodiment of the particletrapping sheet 50 that corresponds to the embodiment depicted in FIG.2B. In comparing the embodiment of FIGS. 5A and 5B, like element numberscorresponding to like features. Therefore this discussion will focus ondifferences. The illustrated particle trapping sheet 50 includesextensions 54 for coupling the particle trapping sheet 50 to a lowerside of the three dimensional article of manufacture 26. The extensions54 may vary greatly in a vertical extent in Z according to a geometry ofthe three dimensional article of manufacture 26. Distal ends 66 of theextensions 54 are of a minimal cross sectional area to facilitate theseparation of the particle trapping sheet 50 from the three dimensionalarticle of manufacture 26. Preferably the extensions 54 are laterallyaligned with ribs 62 to improve structural integrity.

FIG. 6A is a flowchart depicting a process 70 for operating printingsystem 2 to fabricate a three dimensional article of manufacture 26. Allsteps of this process are executed by control server 14 and print enginecontroller 48 that control portions of printing system 2 and printengine 6. Process 70 corresponds to the description of FIG. 2A.

According to step 72, the transport mechanism 12 retrieves a fixture 40from a fixture cassette 4 and loads it into a print engine 6. Thefixture 40 is an embodiment similar to that discussed with respect toFIG. 2A, FIG. 3, and/or FIG. 4. Upon loading the fixture 40 into printengine 6, the movement mechanism 38 can engage and vertically positionthe fixture 40.

According to step 74, the movement mechanism 38 lowers and positions thefixture 40 whereby the distal ends 58 of projections 46 are positionedat build plane 36. Build plane 36 is at an operating distance from thetransparent sheet 20.

According to step 76, the print engine controller 48 operates the lightengine 24 and the vertical movement mechanism 38 to form a particletrapping sheet 50 as is illustrated in FIG. 2A, FIG. 4, or FIG. 5A. Theparticle trapping sheet 50 preferably spans essentially the entire buildplane 36 and is coupled to all of the projections 46. Formation of theparticle trapping sheet traps loose particles that are primarilysolidified photocurable resin. Also as part of step 76, the connectingfeatures 52 are formed that taper downwardly.

According to step 78, the print engine controller 48 operates the lightengine 24 and the vertical movement mechanism 38 to form a threedimensional article of manufacture 26 that couples to the connectingfeatures 52. A lateral cross sectional area over which the connectingfeatures 52 couple to the three dimensional article of manufacture 26 ispreferably minimized to facilitate later separation.

According to step 79, the transport mechanism unloads the fixture 40from the print engine 6 and additional processes are performed. Theseadditional processes can include post processing, inspection, andremoval of the particle trapping sheet 50 from the three dimensionalarticle of manufacture 26. In one embodiment the transport mechanism 12sequentially transfers the fixture 40 to different post process stations8 and inspection stations 10. When the particle trapping sheet 50 isremoved it separates along the lateral area between the connectingfeatures 52 and the three dimensional article of manufacture 26.

In an alternative embodiment the print engine 6 is a standalone unit andsteps 72 and 79 are performed manually. This includes manual loading andunloading of fixture 40 as well as cleaning, drying, UV curing,inspection, and removal of the particle trapping sheet 50.

FIG. 6B is a flowchart depicting a process 80 for operating printingsystem 2 to fabricate a three dimensional article of manufacture 26. Allsteps of this process are executed by control server 14 and print enginecontroller 48 that control portions of printing system 2 and printengine 6. Process 80 corresponds to the description of FIG. 2B.

According to step 82, the transport mechanism 12 retrieves a fixture 40from a fixture cassette 4 and loads it into a print engine 6. Thefixture 40 has a lower face 45 that faces downwardly.

According to step 84, the movement mechanism lowers and positions thelower face 45 of fixture 40 at the build plane 36. The build plane 36 isat an operating distance from the transparent sheet 20. According tostep 86, the print engine controller 48 operates the light engine 24 andthe vertical movement mechanism 38 to form a three dimensional articleof manufacture 26.

According to step 88, the print engine controller 48 operates the lightengine 24 and the vertical movement mechanism 38 to form a particletrapping sheet 50 as is illustrated in FIG. 2B or FIG. 5B. The particletrapping sheet 50 preferably spans the entire build plane 36. Theparticle trapping sheet 50 is coupled to the three dimensional articleof manufacture 26 via extensions 54. The extensions 54 form a frameworkfor properly supporting the particle trapping sheet 50 in the vessel 24.

According to step 89, the transport mechanism unloads the fixture 40from the print engine 6 and additional processes are performed. Theseadditional processes can include post processing, inspection, andremoval of the particle trapping sheet 50 from the three dimensionalarticle of manufacture 26. In one embodiment the transport mechanism 12sequentially transfers the fixture 40 to different post process stations8 and inspection stations 10. When the particle trapping sheet 50 isremoved it separates along an interface between the distal ends 66 ofextensions 54 and the three dimensional article of manufacture 26.

In an alternative embodiment the print engine 6 is a standalone unit andsteps 82 and 89 are performed manually. This includes manual loading andunloading of fixture 40 as well as cleaning, drying, UV curing,inspection, and removal of the particle trapping sheet 50.

FIG. 6C is a flowchart depicting a process 90 for operating printingsystem 2 to fabricate a three dimensional article of manufacture 26. Allsteps of this process are executed by control server 14 and print enginecontroller 48 that control portions of printing system 2 and printengine 6. Process 90 corresponds to the description of FIG. 2C.

According to step 92, the transport mechanism 12 retrieves a disposablefixture 40 from a fixture cassette and loads it into a print engine 6.The fixture can be an embodiment that is similar to that discussed withrespect to FIG. 2C, FIG. 3, or FIG. 4. Upon loading the fixture 40 intoprint engine 6, the movement mechanism 38 can engage and verticallyposition the fixture 40.

According to step 94, the movement mechanism 38 lowers and positions thefixture 40 whereby the distal ends 58 of projections 46 are positionedat build plane 36. Build plane 36 is at an operating distance from thetransparent sheet 20.

According to step 96, the print engine controller 48 operates the lightengine 24 and the vertical movement mechanism 38 to form a particletrapping sheet 50 as is illustrated in FIG. 2C. The particle trappingsheet 50 preferably spans essentially the entire build plane 36 and iscoupled to all of the projections 46. Formation of the particle trappingsheet traps loose particles that are primarily solidified photocurableresin.

According to step 98, the transport mechanism unloads the disposablefixture 40 from the print engine 6. According to step 100, the transportmechanism loads a new fixture 40 into the print engine 6. According tostep 102, the print engine controller 48 operates the light engine 24and the vertical movement mechanism 38 to form a three dimensionalarticle of manufacture 26.

According to step 104, the transport mechanism unloads the fixture 40from the print engine 6 and additional processes are performed. Theseadditional processes can include post processing, and inspection. In oneembodiment the transport mechanism 12 sequentially transfers the fixture40 to different post process stations 8 and inspection stations 10.

FIGS. 7A and 7B are schematic block diagrams depicting an embodiment ofa standalone print engine 6 for manufacturing a three dimensionalarticle 26. FIGS. 7A and 7B illustrate two stages of a manufacturingprocess. The element numbers shown in FIGS. 7A and 7B are the same asthose depicted in FIG. 2A except as discussed infra.

A controller 106 is configured to control the light engine 24, thevertical movement mechanism 38, and to control and/or receive signalsfrom other portions of the print engine 6. The controller 106 is coupledto a user interface device 108. User interface device (referredhereinafter as UID 108) can be a touchscreen permanently coupled to thestandalone print engine 6. Alternatively, the UID 108 can have either awireless or wired connection to the controller 106. The UID can also bea laptop computer, a smartphone, a personal digital assistant (PDA), atablet computer, a desktop computer, a floor standing computer, or anyclient device accessible by a user.

FIG. 7A depicts a first stage of a manufacturing process during whichthe light engine 24 is forming a particle trapping sheet 50 at the buildplane 36. This is illustrated as taking place while the lower face 45 offixture 40 is not immersed in the photocurable resin 18. FIG. 7B depictsa second stage of the manufacturing process during which operation ofthe light engine 24 and the movement mechanism 38 are manufacturing athree dimensional article 26.

FIG. 8 depicts a method 110 of manufacturing a three dimensional article26. The steps of method 110 are generally performed by the controller106. According to element 112, the method starts with the fixture 40raised above the resin vessel 16. Alternatively, the fixture 40 ispositioned whereby the build plane 36 is disconnected from the fixture40 and is not connected to the lower face 45 of fixture 40.

According to step 114, the light engine is operated to solidify aparticle trapping sheet 50 proximate to the transparent sheet 20 asdepicted in FIG. 7A. Any particles that project up from the transparentsheet are “captured” by the particle trapping sheet 50. The particletrapping sheet is disconnected from the transparent sheet 20 anddisconnected from fixture 40.

According to step 116, operation of the print engine 6 is paused.According to step 118, instructions are sent to UID 108 whereby the UIDdisplays instructions to the user of print engine 6 to remove theparticle trapping sheet 50 from the resin vessel 16. After removing theparticle trapping sheet, the user provides an input to the UID 108.According to step 120, the input is received from the UID which signalsthe controller 106 to restart operation of print engine 6.

According to step 122, the movement mechanism 38 is operated to move thelower face 45 of fixture 40 to the build plane 36. According to step124, the light engine 24 and the movement mechanism 38 are operated tomanufacture the three dimensional article 26 as depicted in FIG. 7B.

Variations and/or portions of method 110 can be used. In one embodiment,steps 112, 114, and 118 can be utilized after a particle-based failureis diagnosed. In another embodiment, steps 112, 114, and 118 can beperformed as preventative maintenance that can have a fixed periodicschedule. Other variations are possible that can include more or fewersteps of method 110.

FIGS. 9A and 9B are isometric and side cutaway views of an alternativeembodiment of a support fixture 40 having a central opening 130. Supportfixture 40 includes an upper portion 132 coupled to a lower rim 134 by asidewall 136. The upper portion 132 defines interface features 138 forinterfacing (aligning and coupling) the support fixture 40 with thevertical movement mechanism 38. The sidewall 136 can include openings(not shown) for facilitating movement and draining of the photocurableresin 18 as the lower rim 134 is raised out of the vessel 16.

The lower rim 134 includes an inner edge 142 that bounds the centralopening 130. The central opening 130 spans most or all of the area ofthe build plane 36. The lower rim 134 defines a downwardly facing planarsurface 144 that overlays an outer peripheral portion of the build plane36.

FIGS. 10A-C are a sequence of diagrams representing a verticalcross-section through the support fixture 40 and the three-dimensionalarticle 26 during a manufacturing process. FIG. 10A depicts the supportfixture 40 with central opening 130 before the process has started. Aspart of the process, the lower planar surface 144 of lower rim 134 ispositioned at or proximate to the build plane 36.

According to FIG. 10B, a particle trapping sheet 50 is formed that spansthe central opening 130 and is attached to the lower planar surface 144.The particle trapping sheet 50 is preferably at least one millimeterthick in the vertical direction to provide adequate support for thesubsequent formation of the three dimensional article 26. Thus, sheet 50had a dual role of trapping particles and providing support for thethree dimensional article 26. Sheet 50 preferably includes an array ofconduits that pass vertically therethrough to allow resin to passvertically through the conduits. The conduits can define openings on anupper surface 146 and a lower surface 148 of the sheet 50. The openingscan have varying shapes such as circular, square, rectangular,polygonal, or irregular. In one embodiment, the openings are hexagonaland can form a hexagonal close packed (HCP) pattern across the upper 146and/or lower 148 surface of the sheet 50.

According to FIG. 10C, a three dimensional article 26 is formed onto anddownward from the lower surface 148 of the sheet 50. After the threedimensional article 26 is formed, the sheet 50 can be separated from thesurface 144 and then the article 26 can be separated from the sheet 50.

FIG. 11 is a flowchart that represents an embodiment of a method 150 formanufacturing a three dimensional article 26 that utilizes the supportfixture 40 depicted in FIGS. 9A and 9B. The particle trapping sheetdepicted by method 150 is depicted in any of FIGS. 12-14.

According to 152, the vertical movement mechanism 38 is operated toposition the planar surface 144 at the build plane 36. According to 154,movement mechanism 38 and the light engine 24 are operated to form aperipheral support upon the planar surface 144. The peripheral supportprovides two functions: (1) an attachment support for sheet 50 and (2)adjust for possible inaccuracies in vertical tolerances. The latter is aresult of the difficultly in accurately positioning the planar surface144 exactly at the build plane 36.

According to 156, the movement mechanism 38 and the light engine 24 areoperated to form a particle trapping sheet 50 attached to the peripheralsupport and spanning the opening 130. The particle trapping sheet 50includes fluid passages having lateral geometric aspects that enhanceparticle trapping.

According to 158, the movement mechanism 38 and the light engine 24 areoperated to form tapering supports 52 onto the lower planar support.According to 160, the movement mechanism 38 and the light engine 24 areoperated to form the three dimensional article 26 attached to thetapering supports. Steps 158 and 160 can be performed sequentiallyand/or concurrently.

FIG. 12 is a cross-sectional view of a support fixture 40 with a firstembodiment of a particle trapping sheet 50 that can be formed accordingto steps 152-156 of method 150. A peripheral support 162 has been formedonto the planar surface 144 according to step 154 of method 150. Theparticle trapping sheet 50 has been formed to span opening 130 and ontothe peripheral support 162.

In the illustrated embodiment, the particle trapping sheet 50 defines anarray of conduits 164 that allow resin to flow through the particletrapping sheet 50 as the movement mechanism 38 raises and lowers thesupport fixture 40. The illustrated conduits 164 are oriented at anoblique angle with respect to vertical axis Z in order to morecompletely trap particles. The conduits 164 define openings 166 on theupper 146 and lower 148 surfaces of sheet 50.

FIG. 13 is a cross-sectional view of a support fixture 40 with a secondembodiment of a particle trapping sheet 50 that can be formed accordingto steps 152-156 of method 150. A peripheral support 162 has been formedonto the planar surface 144 according to step 154 of method 150. Theparticle trapping sheet 50 has been formed to span opening 130 and ontothe peripheral support 162.

In the illustrated embodiment, the particle trapping sheet 50 is formedfrom three layers including an upper sheet 50U, a middle portion 50M,and a lower sheet 50L. The upper sheet 50U defines an array of upperopenings 166U. The lower sheet defines an array of lower openings 166L.The upper 166U and lower 166L openings are offset from each other toreduce a chance that particles can escape from being trapped in one ofthe upper 50U and lower 50L sheets. The middle portion 50M defines ribsor beams 168 that help to rigidify the sheet 50 to allow it to support athree dimensional article 26. The middle portion 50M also fluidicallycouples the upper 166U and lower 166L openings. Thus, the three layersof sheet 50 define conduits 164 that pass from the upper surface 146 tothe lower surface 148.

FIG. 14 is a cross-sectional view of the support fixture 40 with a thirdembodiment of a particle trapping sheet 50 formed according to method150. In this illustrated embodiment, sheet 50 includes tapering supports52 coupled to the three dimensional article 26. Otherwise, the thirdembodiment of FIG. 14 is similar to the second embodiment of FIG. 13.

FIGS. 15A-D illustrate steps 154 and 156 of method 150 and correspond tothe particle trapping sheet 50 of either FIG. 13 or FIG. 14. FIG. 15Adepicts the peripheral support 162 that has been formed upon the lowerplanar surface 144 of the lower rim 134. While the peripheral support162 is illustrated as being a rectangular frame in shape, it may be moreeffective if it has a stepped or a zig-zag geometry around the edge 142.

FIG. 15B depicts an upper layer 50U of particle trapping sheet 50 withupper openings 166U. FIG. 15C depicts the middle layer 50M of sheet 50.FIG. 15D depicts the lower layer with lower openings 166L. The upper166U and lower 166L openings are laterally offset from each other toenhance particle trapping. The middle layer defines fluid passages 170that couple the upper 166U and lower 166L openings. Also, support ribs168 are defined between the fluid passages 170.

The specific embodiments and applications thereof described above arefor illustrative purposes only and do not preclude modifications andvariations encompassed by the scope of the following claims.

What I claim is:
 1. A three dimensional printing system formanufacturing a three dimensional article comprising: a resin vessel forcontaining a photocurable resin and having a lower portion with atransparent sheet; a light engine configured to selectively projectradiation up through the transparent sheet and over a build plane; amovement mechanism; a support fixture coupled to the movement mechanismand including: an upper portion for coupling to the movement mechanism;a lower portion with a rim surrounding a central opening; and a sidewall coupling the upper and lower portions of the support fixture; acontroller configured to: (1) operate the movement mechanism to positionthe rim at an operating distance from the transparent sheet; (2) operatethe light engine and the movement mechanism to form a particle trappingsheet that spans the central opening; and (3) operate the light engineand the movement mechanism to form the three dimensional article ontoand below the particle trapping sheet.
 2. The three dimensional printingsystem of claim 1 wherein the controller is further configured tooperate the light engine to form a peripheral support along the rimbetween steps (1) and (2).
 3. The three dimensional printing system ofclaim 1 wherein the particle trapping sheet includes tapering featuresthat taper between the particle trapping sheet and the three dimensionalarticle to facilitate removal of the three dimensional article from theparticle trapping sheet.
 4. The three dimensional printing system ofclaim 1 wherein the particle trapping sheet defines an array of conduitsto allow resin to flow through the particle trapping sheet and throughthe central opening as the movement mechanism raises and lowers thesupport fixture.
 5. The three dimensional printing system of claim 4wherein the conduits individually are at least partially oriented at anoblique angle with respect to a vertical axis to facilitate completetrapping of particles.
 6. The three dimensional printing system of claim4 wherein the conduits individually define an upper opening on an upperside of the particle trapping sheet and a lower opening on a lower sideof the particle trapping sheet, the upper and lower openings arelaterally offset to facilitate trapping of particles.
 7. The threedimensional printing system of claim 1 wherein the particle trappingsheet has a vertical thickness of at least one millimeter to providestructural support for the three dimensional article.
 8. The threedimensional printing system of claim 1 wherein the particle trappingsheet includes a plurality of support ribs to provide structural supportfor the three dimensional article.
 9. The three dimensional printingsystem of claim 8 wherein the support ribs are defined between an uppersheet and a lower sheet that are thinner vertically than the supportribs.
 10. A method of manufacturing a three dimensional article using athree dimensional printing system including a resin vessel forcontaining a photocurable resin and having a lower portion with atransparent sheet, a light engine configured to selectively projectradiation up through the transparent sheet and over a build plane, amovement mechanism, a support fixture coupled to the movement mechanism,and a controller, the support fixture further including an upper portionfor coupling to the movement mechanism, a lower portion with a rimsurrounding a central opening, and a side wall coupling the upper andlower portions of the support fixture, the method comprising: (1)positioning the rim at an operating distance from the transparent sheet;(2) operating the light engine and the movement mechanism to form aparticle trapping sheet that spans the central opening; and (3)operating the light engine and the movement mechanism to form the threedimensional article onto the particle trapping sheet.
 11. The method ofclaim 10 further comprising forming a peripheral support along the rimbetween steps (1) and (2).
 12. The method of claim 10 wherein theforming the particle trapping sheet includes forming tapering featuresthat taper from the particle trapping sheet to the three dimensionalarticle.
 13. The method of claim 10 wherein the forming the particletrapping sheet includes defining an array of conduits to allow resin toflow through the particle trapping sheet and through the central openingas the movement mechanism raises and lowers the support fixture.
 14. Themethod of claim 13 wherein the conduits individually are at leastpartially oriented at an oblique angle with respect to a vertical axisto facilitate complete trapping of particles.
 15. The method of claim 13wherein the conduits individually define an upper opening on an upperside of the particle trapping sheet and a lower opening on a lower sideof the particle trapping sheet, the upper and lower openings arelaterally offset to facilitate complete trapping of particles.
 16. Themethod of claim 10 wherein the particle trapping sheet has a verticalthickness of at least one millimeter to provide structural support forthe three dimensional article.
 17. The method of claim 10 wherein theparticle trapping sheet includes a plurality of support ribs to providestructural support for the three dimensional article.
 18. The threedimensional printing system of claim 17 wherein the support ribs aredefined between an upper sheet and a lower sheet that are thinnervertically than the support ribs.
 19. The method of claim 10 furthercomprising separating the particle trapping sheet from the threedimensional article.